Phosphonic acid dialkyl esters

ABSTRACT

IN WHICH R denotes an alkyl radical with one to 18 carbon atoms and n denotes 1 or 2. These phosphonic acid dialkyl esters are used as antioxidants for plastics, especially for polypropylene, polyethylene and polyurethane, and rubber. The combined use of the phosphonic acid dialkyl esters with flameproofing agents, may increase the flameproofing action of the flameproofing agent. The use of the compounds according to the invention in combination with other antioxidants also may show advantageous effects.   The subject of the invention is phosphonic acid dialkyl esters of the formula

United States Patent 51 July 25,1972

Huber-Emden et al.

[54] PHOSPHONIC ACID DIALKYL ESTERS [21] App]. No.: 5,148

[30] Foreign Application Priority Data Jan. 30, 1969 Switzerland ..l460/69 [52] US. Cl. ..260/943, 117/136, 260/459 R, 260/562 A, 260/562 B, 260/562 S, 260/969 [51] Int. Cl. ..C07f 9/40 [58] Field of Search ..260/943 [56] References Cited UNITED STATES PATENTS 2,875,232 2/1959 McConnell et al ..260/943 X 2,908,605 10/1959 Beriger et al ..260/943 X Primary Examiner-Joseph Rebold Assislan! Examiner-Richard L. Raymond Attorney-Harry Goldsmith, Joseph G. Kolodny and Mario A. Monaco [57] ABSTRACT The subject of the invention is phosphonic acid dialkyl esters of the formula in which R denotes an alkyl radical with one to 18 carbon atoms and n denotes 1 or 2. These phosphonic acid dialkyl esters are used as antioxidants for plastics, especially for polypropylene, polyethylene and polyurethane, and rubber. The combined use of the phosphonic acid dialkyl esters with flameproofing agents, may increase the flameproofing action of the flameproofing agent. The use of the compounds according to the invention in combination with other antioxidants also may show advantageous effects.

10 Claims, No Drawings PHOSPHONIC ACID DIALKYL ESTERS wherein Y denotes a halogen atom, is condensed with (b) a compound of formula The subject of the invention is phosphonic acid dialkyl (8) (--R)a esters of formula wherein R denotes an alkyl residue with one to 18 carbon (1) 0 (CH atoms. This reaction can be carried out without solvents or in a suitable solvent, such as for example xylene. The halogen HOCHz-NHC O(CH ),,l =(O atom Y in the formula (7) can for example represent an iodine or bromine atom or especially a chlorine atom. C(CHJ); The starting product of formula (7) required for this reaction is obtained from 2,6-di-tertiary-butylphenol and N- wherein R denotes an alkyl residue with one to 18 carbon methylol-chloracetamide by Tschemiak condensation. This atoms and n denotes l or 2. latter reaction is known and is described in French Pat.

Preferred phosphonic acid dialkyl esters correspond to the Specification 1,571,696- formulas The compounds offormulas (2), (3), (4) and (5) with n l are accordingly obtained by using, as component (b), a com- (CH3) :4 0 pound of formulas HOOHz-NHCO(CHz)n =(0R1)2 (9) P(-OR (10) 2)a 96. 39 1n a1)s' 4 e)a wherein R, denotes an alkyl residue with 12 to 18 carbon atoms and n denotes l and also wherein R and R have the indicated significance.

(3) C(OHm Phosphonic acid dialkyl esters of formula (1), wherein n 2, are manufactured by reacting (a) a compound of formula C(CH3)3 (13) C(CHah 0 on NH-o O-CH -CH wherein R denotes an alkyl residue with two to four carbon H 2- 2 atoms and n denotes l or 2. axons) Amongst the compounds encompassed by formulas (2) and (3), those of formulas with (b) a. compound of formula C (CH3): ll

I t Lit-3110B HO- CH2-NH -CO(CH2)n' =(OClBHil7)Z whereinR represents an alkyl residue with one to 18 carbon C(CHW f atoms. This reaction'is approximately carried out in an anwherein n denotes 1 or 2 and hydrous medium, for example a suitable organic solvent such as absolute dioxan, tetrahydrofuran or 1,2-dimethoxy-ethane.

(5) 0 (CH3)! 0 The reaction is catalysed by the presence of small amounts of q sodium salt of the corresponding compound of formula (14),

CHFNHfC 1 which is first formed in situ by the addition of metallic sodium.

| The starting product of formula 13) required for this reac- CwHm tion can be obtained from 2,6-di-tertiary-butylphenol and N- methylol-acrylamide by Tschemiak condensation in glacial acetic acid in the presence of pyrophosphoric acid, as has already been described in French Pat. Specification 1,475,097. 0 A more rational route for the manufacture of the compound II of formula (13) consists in the same reaction except for the HO 0H2-NH-0oCHiP=(O C "H") pyrophosphoric acid being replaced by gaseous hydrogen 1 chloride. In this, a 1:1 addition product of the compound of C(CHa)a formula (13) and N-(3,5-di-tertiary-butyl-4-hydroxyphenylis particularly suitab1e methyl )-B-chloropropionamide first precipitates directly:

wherein n denotes 1 or 2, are above all of interest. 50

The compound of formula (15) .NC ah 0 C 3):

( Da N (12D (N07110:

The phosphonic acid dialkyl esters of formula (1) are thus The compounds of formula (13) is obtained in good yields for example dimethyl, diethyl, dibutyl, didodecyl or diocfrom the addition product of formula (15) by splitting ofi l-lCl tadecyl esters. Depending on whether n is 1 or 2, different by means of sodium hydrogen carbonate. starting products are used for the manufacture of these dialkyl The compounds of formulas (2), (3), (4) and (5) with n 2 esters. are accordingly obtained by using, as component (b), a com- If n 1, the procedure followed is that, in accordance with pound of one of the formulas the principle of the Michaelis-Arbusow reaction, (a) a compound of formula (':(CH3)3 v H.IQ=(O4C4H9)Z wherein R and R, have the indicated significance.

The phosphonic acid dialkyl esters of formulas (l) to (6) are used as antioxidants for plastics. Possible plastics are polyethylene, polyurethane and above all polypropylene; further, also polyvinyl chloride and rubber.

When protectingoxidation-sensitive plastics against oxidation,.the appropriate procedure is to incorporate into these plastics a small amount, preferably 0.01 to 2 percent relative to the amount of plastic to be protected, of at least one compound offormulas(1)to (6). V

v The compounds of fonnula (1') can for example be worked into the plastics to be protected directly, that is to say by themselves .or together with other additives such as plasticizers, pigments, light protection agents, fluorescent whitening'agents, flameproofing agents or other antioxidants,

and/or with the aid of solvents. 'The combined use of the compounds of formulas( l) to (6) together flameproofing agents, especially those containing" phosphorus, shows certain advantages, aboveall inpolyuretha necoating compositions. This is because in addition to theactualantioxidant action, the compounds of fonnulas (1) to (6) are also able distinctly to increase the flameproofing action of the flameproofing agent.

The use of the compounds of formulas (1) to (6) in combination with other. antioxidants; namely carboxylic acid amides containing sulphur, have proved particularly advantageous.

These carboxylic acid amides are known from French Pat. Specification 1,571,696 and correspond to the formula wherein R, denotes a benzene residue which carries a hydroxyl group in the o-p'osition or p-position to the CH, group and carries two hydrocarbon residues as further substituent's,

R, denotes a hydrogen atom, an alkyl or aryl residue which is optionally substituted further, or a residue of formula wherein R has the indicated significance and m denotes an integer having a value of at most 2, and n denotes ,an integer h'avinga value of at most 7. Carboxylic acid amides of formula 20), wherein the residue R carries several thioether residues, are preferred. In particular, thioethers of formulas 51.5 g of 2,6-di-tertiary-butylphenol and 26.5 g of N- methylolacrylamide are successively dissolved in 50 ml of glacial acetic acid with gentle warming. Thereafter HCl gas is introduced whilststirring, and with exclusion of moisture, until i saturation is reached. The reaction is exothermic; the temperature is kept at 30 C by external cooling.

During the reaction a thick precipitate forms. Thereafter the mixture is stirred for a further 3 to 4 hours at roomtemperature and then for a further one-half hour at 5 to 10 C. The product is then thoroughly suction-filtered off and rinsed with a little glacial acetic acid. The filter residue is stirred with 1 liter of water, filtered off and rinsed with water. 57.7 g (=75 percent of theory) of the 1:1 addition product of N-(3,5-ditertiary-butyl-4-hydroxypheny1 methyl)-acrylamide and N- 3,5-di-tertiary-butyl-4 hydroxy-phenyl methyl )-fi- 'chloropropionamide are obtained; melting point: 168 to 171 hydrogen carbonate and 200 ml of'acetone is boiled for 1 hour I under reflux whilst stirring. The mixture is cooled, undissolved inorganic material is filtered off and thesolvent is removed in vacuo. The oily residue rapidly crystallizes throughout after seeding. 54 g of N-(3,5-di-tertiary-butyl-4-hydroxyphenylmethyl)-acrylamide of melting point 107 to 109 C, corresponding to formula 13), are obtained.

The product is recrystallized from 400 ml of cyclohexane and 47.1 g (=65 percent of theory, relative to. the 2,6-ditertiary-butylphenol employed) of the acrylamide of melting point 1 12 to 1 13 C are obtained.

The acrylarnide of formula (13) can also be obtained in almost quantitative yield from the 1:1 addition products by vigorously stirring the latter with excess 2N sodium carbonate solution for several hours and washing the product, after filtering off the sodium carbonate solution, until a neutral reaction is obtained; melting point: 110 to 15 C. When manufactured according to this latter method, the substance is not entirely free of bonded chlorine.

chloracetamide are dissolved in 50 ml of dry xylene by warming. 7.22 g of phosphorus acid trimethyl ester are added and the mixture is heated to gentle boiling under reflux. The reaction is complete when the reaction solution contains no further bonded chlorine, which can easily be followed byoccasional sampling and testing by means of the Beilstein reaction. Gentle boiling under reflux for 40 to 45 hours sufl'ices.

Thereafter the mixture is cooled, whereupon the product precipitates after a short time. 16.2 g (=73 percent of theory) of a compound of melting point (after recrystallization from benzene or from xylene) 142 to 143 C are obtained, corresponding to the formula l a)a EXAMPLE 2 An analogous procedure to example 1 is followed, using phosphorous acid triethyl ester (instead of the trimethyl ester) in the stoichiometric amount. Yield: 62 percent of theory; melting point (after recrystallization from xylene or cyclohexane): 97 to 99 C. The compound corresponds to the formula EXAMPLE 3 18 g of N-( 3,5-di-tertiary-butyl-4-hydroxyphenylmethyl)- chloracetamide and 14.6 g of phosphorous acid tributyl ester are heated together for 2 hours to 175 C (bath temperature) in a reflux apparatus, with an air condenser. During the course of this, nitrogen is passed into the reaction vessel in order to expel the resulting butyl chloride through the reflux condenser. Thereafter the mixture is cooled and recrystallized from 80 ml of cyclohexane. g (=73 percent of theory) of a compound of formula (26) are obtained.

A larger sample is chromatographically purified on silica gel using an ascending eluent series of benzenechloroforrn, and is then again recrystallized from cyclohexane; melting point: 91 to 92 C.

EXAMPLE 4 9 g of N-(3,S-di-tertiary-buty1-4-hydroxyphenyl-chloracetamide and 17 g of phosphorous acid tridodecyl ester are heated in a distillation apparatus with a stirrer, at 15 mm Hgpressure, for 2 hours with stirring to 175 C, finally reaching 200 C (bath temperature). In the course thereof, 3.75 g (=63 percent of theory) of dodecyl chloride distil ofi at 135 to 148 C.

After cooling, the residue is chromatographed on silica gel with an ascending eluent series of benzene-chloroform, whereupon 15 g (=75 percent of theory) of a waxy-crystalline product of melting point 47 to 49 C are obtained, corresponding to the formula EXAMPLE 5 l Hsh b. 9 g of N-3,5-di-tertiary-butyl-4-hydroxyphenyl-methyl)- chloracetamide and ml of dry xylene are heated for 90 7 hours under reflux in nitrogen at a bath temperature of 175 C. Thereafter the solvent is removed in vacuo and the waxy residue is purified as described in example 5 a); melting point: 715 to 72.5 C.

Purification can also be effected by chromatography on silica gel with an ascending eluent series of benzenechloroform-ethyl acetate.

The compound of formula (28) is obtained.

EXAMPLE 6 27.6 g of phosphorous acid diethyl ester are dissolved in 150 ml of absolute dioxan. 0.5 g of sodium are added and the mixture is stirred for 15 hours under nitrogen. In the course thereof, the sodium dissolves and a small amount of a flocculent precipitate is produced.

57.8 g of N-(3,5.-di-tertiary-butyl-4-hydroxyphenylmethyl)- acrylamide are now added; this dissolves rapidly and the mixture is stirred for a further 25 hours under closed condition. The solvent is then completely removed in vacuo. The resinous residue is recrystallized from dry benzene and the crystalline product is dried for some time in vacuo. 55.7 g (=65 percent of theory) of the product of melting point 104 to 106 C are obtained, corresponding to the formula C(CHa):

EXAMPLE 7 7.76 g of phosphorous acid dibutyl ester are dissolved in 30 ml of absolute dioxan. 0.1 g of sodium are added and the mixture is stirred under nitrogen for 15 hours; in the course thereof, the sodium dissolves and a small amount of a flocculant precipitate is produced. 11.57 g of N-(3,5-di-tertiarybutyl-4hydroxyphenylmethyl)-acrylamide are now added and dissolve rapidly. Thereupon the reaction mixture, contained in a closed vessel, is stirred for 3 days, and is thereafter heated for a further 2 hours to the boil under reflux, in nitrogen.

The solvent is now completely removed in vacuo and the waxy-crystalline residue is recrystallized from cyclohexane. 12.6 g (=65 percent of theory) of the compound of melting point 113 to 116 C are obtained, corresponding to the formula C(CHa):

EXAMPLE 8 17.6 g of phosphorous acid dioctadecyl ester are dissolved in ml of absolute l,2-dimethoxyethane whilst warming. 70 mg of sodium are added and the mixture is heated for 18 hours under reflux in nitrogen, while stirring. In the course thereof, the sodium dissolves and a small amount of a flocculant precipitate forms. 8.67 g of N-( 3,S-di-tertiary-butyl-4-hydroxyphenylmethyl)-acrylamide are added thereto; this dissolves rapidly and the mixture is heated for 24 hours under reflux in nitrogen.

Thereafter it is left to stand for 2 days at room temperature under closed conditions, whereupon a large part of the product crystallises out. crystallizes further proportion is obtained by concentrating the mother liquor.

the compound of melting point 76 Purification is effected by recrystallization from a large amount of petroleum ether. 15.3 g (=58 percent of theory) of to-78 C, corresponding to formula (31 are obtained.

1t is also possible to dissolve the crude product in chloroform and then to purify it by chromatography on silica gel. Hereupon, the substanceis obtained as a chloroform adduct; melting point 35 to 36 C, the product resolidifies on further heating and finally melts at 72 to 74 C. The chloroform can be eliminated from this adduct by heating in a high vacuum (at 160 C/ 10 minutes/0.001 mm Hg.).

EXAMPLE 9 A mixture of 20 percent of the thioether of formula (22) or (23) and 80 percent of the phosphonic acid dialkyl ester of formula (27) is heated with stirring, under a nitrogen atmosphere, for; 1 minute to 130? or 165 C respectively, whereupon cloudy to clear melts are produced. The mixture is then quenched'by cooling with cold water.

The following combinations were obtained according to this process:

TABLE 1 Mixture Thioether Phosphonic acid Consistency of formula dialkyl ester of formula v A (22) (27) Resinuous B (23) (27) Resinous TEST OF ANTIOXIDATIVE EFFECTIVENESS thick sheet. The sheet is cut into narrow strips and is left to age 1 in an oven at 140 C until distinct cracks can be detected visually.

The results are summarized in table 11. For comparison, the ageing times achievable with the thio compounds of formula (22) or (23) alone are also given. It can be seen from the figures that the combination of the phosphonates with the thio compounds give even better protection against ageing than the individual compounds alone.

Mixtures of 100 parts of rubber (latex crepe), 5 parts of zinc oxide, parts of titanium dioxide. 75 parts of barium sulphate, 1 part of stearic acid, 1.5 parts of Z-mercaptobenz'thiazole, 2 parts of sulphur and 1 part of one of the compounds of formulas (25), (26), (27), (30), (31) or of combination B (see example 9) are homogeneously mixed on a two-r011 mill at 60 C for 30 minutes and subsequently pressed to give 1 mm thick sheets by vulcanization for minutes in a press at 140 C. Dumb-bell-shaped 8 cm long 5 pressed specimens are punched from these and are then aged for 50 hours in an oven at 100 C. The decrease in the mechanical strength and the antioxidant action of the abovementioned compounds can be recognized by measuring the breaking load and elongation at break before and after ageing.

10 The results are summanz' ed in table 111. The figures given are in each case average values from 5 tests at a time. i

In table 111 the symbols denote: L= breaking load in kp/mm l5 D= elongation at break in I;

TABLE I11 Antioxidant of v I 20 Mechanical oven ageing, 100 C Decrease formula, or strength urs in I: combination '50 Without L 1.29 1.03 20 additive D 910 772 20 D 934 8 14.3 (27) L 1.51 1.33 12 o 1012 877 13.2

(30) L 1.48 1.39 6 D 932 802 14 (31 L 1.24 1 l l l D 930 772 17 B L 1.31 l. l 8 10 D 944 824 12.7

EXAMPLE 1 1 v 100 parts of polyethylene granules 'are mixed dry with 0.2 part of one of the compounds of formulas (25), (26), (27),

(28), (29), (30), (31) orofcor'nbinat'ions A or B, and are subsequently processed on a tworo1l mill at 140 C for 3 minutes to give a homogenous hide. This is then pressed in a press at 150 C for 5 minutes to give an 0.2 mm thick foil. The dumbbell-shaped 8 cm long test specimens required for the tear tests are punched therefrom and are then aged for 200 hours in an oven at 85 C. The decrease in mechanical strength and the antioxidant action of the abovementioned compounds can be recognizedby measuring the breaking load and elongation at break.

The results are summarized in table IV. The values given are in each case average values from 5 samples at a time.

The symbols denote: L breaking load in kp/mm D= elongation at break in k TABLE IV Antioxidant of 9 Mechanical Oven ageing, 85 C Decrease formula, or strength hours in I: combination 0 200 '65 Without L 1.38 1.06 23 additive D 370 248. 33

(25) L 1.44 1.32 8.2 D 397 380 4.2 (26) L 1.43 1.30 9

D 440 399 9.3 (28) L 1.39 1.18 l 5 D 381 327 14.2 (29) L 1.5 1.21 19.3 D 433 378 12.6 (30) L 1.45 1.21 16.5 D 428 346 19 D 407 330 19 A L 1.54 1.29 16 100 parts of polyethylene powder are mixed dry with 0.2 part of one of the compounds'of formulas (25), (26), (27), (28), (29), (30) or of combinations A or B and subsequently processed for 3 minutes on a two-roll mill at 1 C to give a homogeneous hide. This is then pressed in a press at 130 C for 3 minutes to give a 1 mm thick sheet which is aged for 72 hours in an oven at 85 C. For determining the melt index, the sheets aged in this way are comminuted into small chips. The melt index is detennined according to ASTM D-l238-62 T, method E (weight 2.16 kg, temperature 190 C, time 10 minutes). The increase in the melt index and the antioxidant action of the abovementioned compounds can thus be recognized. The results are summarized in table V.

TABLE V Melt index in grams Oven ageing, 85 C Antioxidant of formula or combination 5 percent of the compound of formula (25) or (29) or of the mixture consisting of 1 part of one of these compounds and 9 parts of commercially available flameproofing agent of formula bis-(Z-hydroxy-ethyl)-amino-methane-phosphonic acid diethyl ester are stirred into a polyurethane coating composition of g of isocyanate-modified polyester, 1 g of reaction accelerator, l g of polyfunctional isocyanate as a crosslinking agent and 5 ml of ethyl acetate. These mixtures are applied as a thin layer (0.5 mm) on flameproof cotton fabric by means of a doctor blade and cured in air at room temperature. The test specimens manufactured in this way are subjected to the flame test according to DIN 53906, oven ageing at 85 C and exposure to light in the Xeno test.

It can be seen from the results of table Vl that an admixture of the compounds of formulas or (29) to the flameproofing agent considerably increases its flameproofing action.

ethylamino- Burns off methane-phosphonic acid diethyl ester FSM) 4.5% FSM 0.5% of the Self-excompound of tinguishing formula (25 very yellow Yellowish.

Trace Colorless yellow 4.5% FSM 0.5% of the Self-ex- Trace Colorless compound of tinguishing yellow formula (29) We claim:

1. A phosphonic acid dialkyl ester of the formula 7. The compound according to claim 1 of the formula 8. The compound according to claim 1 of the formula 9. The compound according to claim 1 of the formula C(CHa):

10. The compound according to claim 1 of the formula 

2. A compound according to claim 1 in which R is an alkyl radical with 12 to 18 carbon atoms.
 3. A compound according to claim 1 in which R is an alkyl radical with two to four carbon atoms.
 4. A compound according to claim 1 in which R is -C18H37.
 5. A compound according to claim 1 in which R is -C4H9.
 6. The compound according to claim 1 of the formula
 7. The compound according to claim 1 of the formula
 8. The compound according to claim 1 of the formula
 9. The compound according to claim 1 of the formula
 10. The compound according to claim 1 of the formula 